1. Field of the Invention
The embodiments described herein relate to microscope observing systems, and more particularly to methods for scanning large sample areas using a microscope observing system.
2. Background of the Invention
In a conventional microscope observing instrument, the sample or object to be observed is placed on a moving sample stage that can be manually adjusted or automatically manipulated, e.g., by a servo driven apparatus. Such conventional microscope instruments comprise an optical axis that is fixed in a single direction or position for viewing the sample. To change the position of the sample relative to the fixed optical axis, the sample stage holding the sample is set into motion, e.g., the sample stage is a moving sample stage, in such a manner as to place the sample in the correct observation position relative to the optical axis.
The moving sample stage is often permanently attached to the microscope instrument frame. Further, conventional microscope instruments often comprise an objective that remains stationary, or in a fixed optical axis, while the sample stage moves the sample relative to the fixed optical axis.
In certain instances, it is necessary to observe large sample areas. This can pose problems for conventional microscope observing instruments, because the sample must be moved in a coordinated fashion to allow efficient viewing of the entire sample. For example, it can be desirable to use scanning microscope technology to scan specimens or surfaces for computer aided or visual analysis. Further, such systems can be used for guiding and controlling through the use of imagery, e.g., a surgical laser, a mechanical cutting device, or other diagnostic device.
One of the challenges of observing a large sample area is the small available field size of the observing apparatus at high magnifications. No single optical element exists that allows viewing of all of the large areas at one time. There are several conventional devices in use that attempt to provide the scanning ability required. Certain of these devices are generally known as gantry microscope or as scanning probe microscope observing instruments. This type of instruments use a probe permanently fixed in a single observing axis or position and scan the probe over the sample under observation in a defined area.
These conventional devices have several drawbacks however. For example, a gantry microscope is supported by multiple assemblies and lacks the freedom or ability to observe samples in free space due to having one or two fixed observing axis. In general, conventional microscope observing instruments do not have the ability to freely translate or rotate into different observing orientations and are fixed in space with a defined, and thereby limited, sample area size, sample physical dimension, and locations of the sample.
A scanning probe microscope observing instrument uses a single point source of coherent radiation, or an Atomic Force Microscope (AFM) mechanical sensing tip that must physically contact the sample. Alternatively, such instruments can use capacitance properties or acoustical energy to build an image through software manipulation, but such instruments are not optical microscope observing instruments.
Conventional scanning probe microscope observing systems also do not provide a real-time full field of view, cannot be positioned to look at samples located away from the instrument base, cannot be oriented by design to any orientation 360 degrees about the optical observing axis, and are not freely supported in space.
A type of microscope observing system known as a scanning microscope does have the ability to scan a sample by taking individual frames and constructing them into a useable format that provides a full view of the sample. Scanning microscopes can, for example, be used to evaluate large areas of a sample to identify specific objects contained in large populations of other objects in a sample using image recognition software. But using conventional scanning microscopes for such applications can be very time consuming and can reduce the throughput of the sample process.
Conventional scanning microscopes are limited due to their form factor in the size of the sample they are able to process. Large asymmetrical objects can not be observed on a conventional scanning microscope due to size limitations. Continuous surfaces larger than 25 mm can not be observed in conventional scanning microscopes at useful magnification, such as those samples that might be encountered in a high magnification analysis of a metallurgical or material sample or surface.